1. Field of the Invention
The invention is generally related to microscopic analysis of concrete. Particularly, the invention is directed to a great improvement of the contrast of concrete cracks and air voids versus the body of concrete for the purpose of automated analysis of concrete microscopic images.
2. Description of the Relevant Art
Air voids and cracks strongly influence the durability and mechanical attributes of concrete. Microscopic techniques are used to analyze the pore system and cracking characteristics of concrete. Available techniques rely on an operator who visually identifies concrete pores and cracks under microscope. U.S. Pat. No. 5,262,967 to Jaber and Pearson discloses a system and method for determining the air-void or aggregate content of concrete under microscope. This system requires an operator to identify features of interest (voids and aggregates) under microscope. In order to apply modern image analysis techniques to microscopic investigation of concrete, there is a need to create a sharp contrast between features of interest (air voids and cracks) and the body of concrete in microscopic images.
It is an object of this invention to provide concrete microscopic images which exhibit a sharp contrast between air voids and cracks versus the body of concrete.
It is another object of this invention to impregnate concrete with liquids which harden within concrete pores and cracks, and produce a sharp contrast with the body of concrete under microscope.
It is another object of this invention to impregnate concrete with liquids which preferentially fill air voids and cracks, but not capillary pores, with substances exhibiting a sharp contrast with the body of concrete.
Applicant has discovered that, for the purpose of fluorescent microscopy, sequential impregnation of concrete first with an ink and then with a polymer containing fluorescent dye mitigates impregnation of capillary pores with fluorescent-containing polymer. Only air voids and cracks are thus impregnated with polymer containing fluorescent dye. After curing of the polymer, therefore, fluorescent cracks and pores exhibit a sharp contrast against the body of concrete in fluorescent micrographs.
For the purpose of scanning electron microscopy, impregnation of concrete with molten metal fills cracks and air voids, but not the capillary pores, with molten metal. After solidification of molten metal scanning electron microscopic images of concrete exhibits sharp contrast between air voids and cracks (which are filled with metal) against the body of concrete.
According to the invention, there is provided concrete impregnation techniques which produce a sharp contrast between air voids and cracks against the body of concrete.